The long term goal of this research is to understand human T cell recognition of antigens restricted by class II MHC molecules. Current knowledge of the structure of the T cell antigen receptor (TcR) and techniques for cloning the genes that encode it now make it possible to analyse the use of specific genes in normal and pathological T cell responses. There are no data yet in man on the diversity of TcR used in response to exogenous antigens. This information is particularly important in view of current strategies to develop peptides with limited numbers of epitopes both as vaccines and potentials immunosuppressants. In autoimmune diseases, a central question is whether specific TcR genes play a role in immune-mediated tissue injury. To approach these issues, we propose analysis of TcR V gene usage by insulin-specific human T cell clones. Insulin is a particularly useful defined protein for studies of human T cell antigen recognition. Therapy with beef/pork insulin mixtures clearly leads to expansion of T cells recognizing limited epitopes on these foreign antigens. In addition, T cells from both treated and untreated diabetics recognize autologous as well as foreign insulins. While the target antigens of T cells in the autoimmune prodrome of type I diabetes are still undefined, They may include insulin as well as islet cell antigens. The human T cell response to insulin thus provides a system for examining V gene usage in response to both exogenous and endogenous antigens. From T cells specific for insulin, derived from treated diabetics, we will isolate cDNA, clone and sequence the alpha and Beta chain genes of their TcR. V region probes derived from these genes will be used to determine whether V gene usage is conservative in cells recognizing autologous versus foreign antigen. Finally, insulin specific T cells will be derived from high risk family members of type I diabetics to examine V gene usage in response to purely endogenous antigen.